Navigation or tracking of instruments during surgical procedures has become increasingly popular. Surgical navigation can help surgeons avoid delicate neural or vascular structures when moving instruments within a patient. In spinal surgery, for example, a surgical navigation system can be used during disc removal, bone drilling, implant insertion, e.g., screw and/or cage insertion, and other steps of the surgery. Use of surgical navigation systems can also reduce the amount of X-ray exposure to which the patient and operating room staff are exposed.
A typical navigation system includes an array of markers attached to a surgical instrument, an imaging system that captures images of the surgical field, and a controller that detects the markers in the captured images and tracks movement of the markers within the surgical field. The controller associates a reference frame of the imaging system with a reference frame of the patient and, informed by a known geometry of the array and the instrument, determines how the instrument is being moved relative to the patient. Based on that determination, the controller provides navigation feedback to the surgeon. The arrays can have different types or geometries, which can vary based on the type of surgery and/or location within the patient that is being tracked.
The precision of the navigation system strongly depends on the design of the tracked instrument. Welding or integrally-forming the navigation array to the instrument can result in relatively high precision being achieved. Such solutions can be inconvenient, as the capability to decouple the array from the instrument or to couple the array to other instruments is absent. Further, arrangements having the navigation array integrally-formed with the instrument can require separate instruments for standard and navigation use, thereby raising costs for equipment.
A number of solutions have been developed to allow the navigation array to be interchangeably attached with one or more instruments. For example, these solutions can include interfaces that have dovetail or v-groove geometries to connect the navigation array to the instrument. These solutions can be geometrically overdetermined, which can make it difficult to consistently and repeatably attach the array and the instrument in a desired relative position and orientation. As a result, these solutions can allow for situations in which the navigation array is not defined in one or more degrees of freedom, which can undesirably reduce the precision of the navigation.